1. Field of the Invention
This invention relates to utilities conservation and replenishment in evaporative apparatus.
More particularly, the present invention relates to conservation in cooling towers and similar apparatus requiring coolant replenishment and treatment.
In a further and more specific aspect, the instant invention concerns a method and apparatus for conservation of materials and energy relating to coolant or water replenishment and chemical treatment in maintaining a predetermined coolant level in reservoirs for cooling towers.
2. Prior Art
Cooling towers of great variety in construction and purpose are often employed for dissipating heat, either generated within a structure or to reduce the interior temperature below the ambient level. Examples include cooling towers, single and multistage evaporative coolers, evaporative condensers, air washers and the like. A feature common to such systems is a reservoir containing a volatile fluid such as water. The fluid is drawn from the reservoir, is subsequently applied to a heat exchanger and removes heat therefrom. At least in part, the removal of heat is effected through evaporation of the fluid, which phase change absorbs relatively large amounts of thermal energy or heat at the expense of some fraction of the fluid. This fraction is lost as vapor in the exhaust from the cooling tower.
Accordingly, it is often necessary to replenish the fluid stored in the reservoir in order to maintain operation of the cooling tower. Typically, some level sensing device is employed in order to determine when to supply replacement fluid to the reservoir and to regulate the rate or frequency with which fluid is replenished. A problem which has been encountered with such approaches is a tendency for the combination of make-up source and level sensing device to "dither" or oscillate about or near a desired equilibrium water level. Such oscillations result in frequent replenishment cycling, causing unnecessary wearing of the mechanism employed to deliver make-up fluid to the reservoir and also engendering waste of coolant fluid added to the reservoir.
Coolant towers are generally provided with water as a coolant fluid, because water is relatively inexpensive, is readily available in urban areas and has a relatively large heat of vaporization, with vaporization occurring in a useful temperature range. However, water supplied or available in many areas contains suspended and/or dissolved materials including minerals, which tend to become concentrated in cooling tower reservoirs because these materials are not carried away by the evaporative process. These materials may increase in concentration to levels where precipitation of dissolved materials and settling of suspended materials cause fouling of portions of the cooling tower apparatus, hindering operation of pumps and the like and also coating the heat exchanger and thereby reducing the efficiency of heat transfer from the coolant circulating therethrough.
Further, the level sensing apparatus employed for regulating the replenishment of fluid within the reservoir may be affected, resulting in improper operation and a failure to maintain the desired predetermined coolant level in the reservoir. This may cause overfilling and therefore waste of make-up fluid or may result in inadequate fluid levels within the reservoir, resulting in reduced cooling capacity.
Accordingly, it is desirable to dilute the body of water accumulated in the reservoir from time-to-time by adding an amount of water thereto. However, this alone is not necessarily sufficient because the concentration of impurities carried in the water and deposited in the reservoir increases as the evaporative processes continue. Therefore, it is appropriate to release or "bleed" some amount of water from the reservoir from time-to-time in order to maintain impurity concentrations within some predetermined limits. Excessive bleeding results in reduced concentration increases but raises operating costs by requiring additional water and also results in increased sewer usage with attendant costs for wastewater treatment and disposal. Inadequate bleeding results in increased impurity concentrations and attendant fouling of the heat exchanger, pumps, plumbing and level regulating assembly. Accordingly, automated bleeding in the proper amount is strongly desirable.
An additional problem often encountered in cooling towers employing water-filled reservoirs results from the fecundity which such an environment provides to a variety of simple organisms. These organisms may include algae, yeasts or fungi as well as single- or multi-celled life forms including bacteria.
Some such organisms may be pathogenic and hence extremely undesirable, particularly in cooling towers employed to provide cool air to structures containing large numbers of people, such as hospitals, hotels, airports, shopping malls, stores, restaurants and other public and private institutions. Legionella, for example, is an organism known to reproduce readily in a cooling tower environment and capable of providing deadly airborne disease when present in such an environment. Another example of airborne disease readily spread by building ventilation is tuberculosis.
A further problem is that algae or fungi, if present in sufficient numbers, may cause fouling of pumping apparatus, level sensing apparatus or heat exchanging apparatus. Such fouling gives rise to attendant undesirable effects as noted with respect to mineral deposits.
In order to combat these varied problems, some form of biocide or chemical inhibitor is often added to the water in the reservoir. Such additives tend to become concentrated in the reservoir in a fashion analogous to that of waterborne minerals and may result in similar unwanted and undesirable effects for much the same reasons. Additionally, the biocide or chemical inhibitor constitutes an added expense associated with maintaining and operating cooling towers. It is extremely desirable to regulate the addition of such materials in order to maintain a useful concentration thereof, thus inhibiting unwanted proliferation of undesirable or damaging micro-organisms, while avoiding unnecessarily high concentrations and the attendant problems and expenses associated therewith.
The prior art has also provided variations of the above described apparatus for cooling towers.
While the various mentioned prior art devices function as apparatus for supplying additional fluid to cooling tower reservoirs, certain inherent deficiencies preclude adequate, satisfactory performance for the purpose of reducing operating expenses and conserving materials and energy required for normal operation.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide improvements in cooling tower operation.
Another object of the present invention is the provision of an improved control system for regulating supply of make-up water to cooling tower reservoirs.
And another object of the present invention is to provide an improved control system for regulating bleeding of stored water from cooling tower reservoirs.
Still another object of the present invention is the provision of a method for conserving supplies while maintaining operating conditions for cooling tower reservoirs.
Yet another object of the instant invention is to provide a method for conserving water in cooling tower heat exchanging apparatus.
Yet still another object of the instant invention is the provision of a method for regulating bleed rate in coordination with supplying make-up water in heat exchanging devices.
And a further object of the invention is to provide a method for coordinating biocide addition to cooling tower reservoirs.
Still a further object of the immediate invention is the provision of a control system for controlling addition of make-up water and also chemical additives to aqueous reservoirs for heat exchanging applications.
Yet a further object of the invention is to provide a control system and method for conservation of make-up water in reservoirs of cooling towers by regulation of both influx and exhaust rates for coolants employed therein.
And still a further object of the invention is the provision of method and apparatus, according to the foregoing, which is intended to maintain predetermined levels of coolant in a reservoir while reducing deposition of mineral materials, inhibiting micro-organism reproduction and simultaneously conserving supplies.